Classic UK Minitrix Models  -  Black 9F
Transmission

I wasn't going to do this section. Years ago, I took my damaged 9F apart, and it took me ages to put it back together again. More recently, I had another go, but in the meantime, various bits had gone missing. Last night, I wasn't happy with the way it was running, so I took it all apart again, cleaned it up, lubricated bits and put it all back together again. About 2 hours in total - and that was taking pictures as well. It now runs more smoothly than my newr 9Fs.

Easy when you know how. So here's how:

All of the bits spread out. I didn't desolder the motor - you can see these bits disconnected in the 'Motor' section. The eccentric valve rod is broken off and missing on both sides of this loco. I've even dismantled the tiny reduction gear and spindles from the motor housing (2 tiny plastic cogs). Note the plastic pins from the centre wheel which used to be attached to the eccentric valve gear.

 

A photo from the right side showing the position of the reduction gears and the locating spindles. The spindles are a tight push fit into the chassis - but can be ejected with a firm push from a narrow bladed screwdriver. It is useful to do this to be able to clean them up, ensure that there is no damage to the teeth or hubs, regrease them and replace them in better shape than they were. If removing the motor, the black wire needs disconnected from the tender. (Cut it inside the tender and resolder it later). The motor and the pickups can be taken off in one piece by unscrewing the 2 motor screws (see motor section) and unscrewing the single cheese head screw shown in the photo.

If removing the motor, the black wire needs to be disconnected from the tender. (Cut it inside the tender and resolder it later). The motor and the pickups can be taken off in one piece by unscrewing the 2 motor screws (see motor section) and unscrewing the single cheese head screw shown in the photo. Keep the wheels axles in pairs with the coupling rods in place. The pair at the rear have tyres, the pair at the front don't. The middle axle has a square hole in the wheel for the crank rather than the round hole for the retaining pin, and it has a larger plastic balance weight moulded into the spokes.

Re-assembling the reduction gearing. The pins help to keep things in approximately the right place. The gearbox is quite wll protected, so I haven't bothered too much about the surplus grease. When the axles are in place, these stay firmly clamped in the frame, and the cogs spin on the static axles.

A better shot to show which gear goes where. The larger of the two has just one cog and a larger hub on one side. The photo is taken looking from the front of the loco.

A shot taken from underneath the chassis before the cogs were firmly located on pins or axles. Front is to the right of the photo. The right side of the loco is at the top of the photo. Use long nosed pliers to hold the axle by one end, and place it in the hole just enough to hold it in position. With a light, look at the cog though the axle hole from the other side. Use the pin to make sure that they are aligned, and then firmly push the axle though.

 

 

 

Inserting the wheels and gears looks easy, but is quite tricky. Place all 4 gears into their (deeper) slots. Start with the rear set of wheels (they have tyres). Remove the connecting rod from one side only - prise the pins out by twisting a screwdriver between the wheel and the coupling rod. (see photos in the Dismantle section of the Mallard). Drop the first axle into place (check the spare end is facing the middle axle position), and rotate the wheel so that the crankpin hole is at the 12 o'clcok position. Easy. Now drop the 2nd axle in. Then spend a bit of time ensuring that the hole is at 12 o'clock. As you do so, note that as you rotate the wheel, the plastic cog will rise out of its slot, and the axles will rise out of theirs. When you think you have them both correct, push the downwards on the gears to make sure that they are seated, and check the positions again.

Now with two wheels and one red cog to keep in place, repeat the operation for the middle axle.

Then with 3 axles and 4 cogs to hold, drop in the other pair of wheels (Again easier if you remove the coupling rod from one side (the same side as before !). Each time, ensure that the wheel is in its proper position before moving to the next wheel. You have to do them in sequence - rear to front or front to rear. Note that there is a little play in each axle/cog. Make sure that all of the slack is taken up in (say) the clockwise direction, before checking the alignment. And keep checking that the axles and cogs are pushed down fully into their slots.

You may wish to place the bottom plate in position after fitting 3 axles so that you can be sure that the rear 3 are definitely properly located, before moving on to the front pair of axles. Removing the bottom plate again without lifting the axles can be tricky though.

As a final check that all 5 wheels are properly postioned, turn the engine round and look at the other side. Whatever the position, the spare end of the coupling rods should be hovering over the hole in the centre wheel, and the coupling rods should form a straight line across all 5 wheels. If not, something is mis-placed ! Ensure that the alignment is not caused by some wheel being turned one way against the free play while others are turned the other way.

 

And don't forget to check that all of the axles and all of the cogs are seated fully. Worth doing at this stage is to check that everything runs smoothly by running a level surface or bit of track across the wheels. Pressure on the wheels will keep the cogs in place. Fit the bogie, making sure the chassis contact is properly positioned. Fit the base plate - press down the centre and then work towards the holes - and then try the run test with the loco the right way up. Try it on the track too - but don't overdo the pressure which could dislodge older, stretched rubber tyres. If all is Ok, refit the coupling rods and pins, and try the test again.

Now refit the contact strip. The plastic base fits into two small locating slots near the front. Make sure that all 6 contact points sit on the flange edges before pressing it into place. They can slip behind the wheels. Use tweezers to straighten the tabs which support the contact strips if necessary - they should protrude horizontally from the main copper strip. I'm not sure what the two tags near the gearbox are for. When in position, screw down the circuit board - as always, insert the screw in the board and offer both up to the threaded hole. It saves trying to fiddle with big fingers and tiny screws in tight places.

Maintaining Classic UK Minitrix Locos
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